One of the major pursuits of science has always been classification. Thanks to Linnaeus, the predominant taxonomy tends to be a fixed hierarchy (ie kingdom – class – order – genus – species). Thus a major pursuit of linguists has been the classification of languages and dialects into such groupings of parent-child (genetic) relationships. These groupings are usually based on the similarities between languages/dialects. However, it is difficult to determine whether a given similarity is a result of common ancestry or merely the influence of one language on another, or even just chance. Thus the preferred method is to group languages based on only shared innovations. Further, morphology is more useful for such analysis than phonology or lexicon.
In this article, Faber outlines the traditional approach to the Semitic languages as well as a new approach first introduced by Robert Hetzron based on shared innovations. The traditional grouping of the Semitic languages tended to be based more on cultural and geographical than linguistic features. The major groups are East Semitic (of which only Akkadian and Eblaite are attested) and West Semitic. West Semitic is further divided as follows:
Modern South Arabian
Old South Arabian
The major change introduced by Hetzron (and modified by Huehnergard) is to group Arabic and Northwest Semitic together under the label Central Semitic, which is distinguished from South Semitic (Southeast Semitic in the traditional model). Arabic shares features with both Northwest Semitic and South(east) Semitic, thus classification depends on which of these features are shared innovations and which may be the result of chance or structural similarities in the languages.
The features Arabic shares with Northwest Semitic include:
1. The realization of the emphatic consonants through pharyngealization (in Ethiopian and Modern South Arabian they are followed by a glottal stop).
2. The prefix conjugation yaqtulu which replaced the form yaqattal with doubling of the middle radical, attested in Akkadian (iparras), Ethiopic, and South Arabian.
3. Levelling of the prefix vowels. In Akkadian the prefixes of the active, non-derived stems are ˀa and ta, but ni and yi. However, in Central Semitic, all of the prefixes for a particular verb stem have the same vowel, either a or i. The vowel a was generalized in Arabic, while Hebrew preserves the a-i alternation (yilmad but yåqum).
4. Generalization of -t- in the kataba suffix conjugation. In the Akkadian stative, the 1cs form is parsā-ku while the 2ms form is parsā-ta. In Hebrew, Aramaic, and Arabic, the 1cs suffix form becomes katab-tu on analogy to the 2ms form katab-ta. In Ethiopic the reverse occurs as the 2ms becomes -ka.
5. Development of the compound negative marker *bal. Farber suggests that these forms may have developed from an inherited Afroasiatic negative particle *b combined with either negative or asseverative *la.
The features that Arabic shares with South(east) Semitic include:
1. The unconditioned sound change *p > /f/.
2. The existence of verbal stems with a long first vowel – kātaba, takātaba.
3. The broken plural, ie plurals formed by adding a prefix and/or internal changes rather than adding a suffix.
Those who group Arabic with South(east) Semitic (Blau, Diem) argue that the first five features represent convergence or diffusion, while the last three are shared innovations. Those who group Arabic with Northwest Semitic (Hetzron, Huehnergard, Goldenberg) argue that the first five are shared innovations while the last three represent common retentions from an older phase of language which have been replaced in Akkadian and Northwest Semitic.